The invention relates to an energy supply device for an electromagnetic valve control of an internal combustion engine.
This application claims the priority of 19,832,874.5, filed Jul. 22, 1998, the disclosures of which is expressly incorporated by reference herein.
Energy supply device serve to feed the electromagnetic valve control of an internal combustion engine of a motor vehicle with electrical energy over the entire speed range, including the starting operation. An electromagnetic valve control requires an approximately fixed operating voltage, consumes high levels of current and has an engine-speed-dependent power requirement of several kilowatts. For the generation of electrical energy in motor vehicles, generators and energy stores, for example batteries, are used. However, the output voltage and power of a generator are speed-dependent. Because the electrical power and voltage provided by the generator and battery generally do not satisfy the requirements of an electromagnetic valve control over all speed ranges, it is expedient to have a special supply circuit between the electromagnetic valve control and the generator, along with the battery.
A generator system including two generators is known from U.S. Pat. No. 5,097,165 which provides supply voltage for consumers of electrical energy in a motor vehicle; virtually speed-independent. A first generator serves for generating a first, lower output voltage. A second generator generates a second, higher output voltage. Each generator is assigned a voltage regulator, by means of which the current in the field windings of the generators is controlled. When the engine is running and there is a changing load, the voltage in both onboard electrical systems can be kept approximately constant.
DE 42 25 515 A1 discloses a device for increasing the generator output voltage in a motor vehicle. The fact that the output lines of the stator winding system of the generator can be switched to earth potential by means of transistors allows the generator output voltage to be briefly increased if required by means of induction voltage pulses.
EP 0 390 398 B1 discloses a starter system for an internal combustion engine which comprises a DC/DC converter for boosting the battery voltage using a storage capacitor. This converter comprises a transformer, the primary winding of which is connected, on the one hand, to the positive terminal of a battery and, on the other hand, via a pulse-triggered transistor switch to earth. The winding ratio of the primary winding and secondary winding is fixed so that the battery voltage is thereby converted from 12 V to 14 V, in order to charge the capacitor initially at the beginning of a starting operation.
The present invention is based on the technical problem of providing an energy supply device for an electromagnetic valve control of a motor vehicle which can be realized with relatively little expenditure and supplies the electromagnetic valve control with electrical energy adequately and effectively over the entire speed range of the internal combustion engine as well as during the starting operation.
According to one aspect of the present invention the energy supply device is parallel to a first diode arrangement, which, as an anode part, lies opposite a second diode arrangement acting as a cathode part. A third diode arrangement is also provided. An electrical energy store is connected to the output of the third diode arrangement. The energy supply device has a controllable DC/DC converter which is connected, on the one hand, to the third diode arrangement and, on the other hand, to the supply output for the electromagnetic valve control.
According to another aspect of the present invention, an energy supply device electrical energy store is connected to the output of the first diode arrangement. The energy supply device has a controllable DC/DC converter which is connected, on the one hand, to the output of the first diode arrangement and, on the other hand, to the supply output for the electromagnetic valve control, a diode being connected parallel to the DC/DC converter. In the present case, apart from actual diode elements, it is possible for POWER-MOS transistors and other semiconductor switches, for example, also to be used as the diode arrangement or diodes.
According to the present invention a fuel-saving energy supply device which provides a stable DC voltage supply for an electromagnetic valve control is provided. By controlling the DC/DC converter, the electromagnetic valve control can be fed electrical energy from the generator and/or the energy store. This makes it possible in ranges of the engine operating map in which disproportionately more fuel is required for generating an excess power for driving the generator or in which the so-called conchoid curve of the generator, which describes its speed-dependent power characteristic, is unfavourable to generate as little electrical energy as possible with the generator and to feed the electromagnetic valve control to the greatest extent from the energy store, which may comprise one or more storage units. Conversely, in ranges of the engine operating map favourable for the generation of electrical energy, i.e. in favourable regions of the conchoid curve of the generator, an excess power can be generated with the generator in order to charge the electrical energy storage unit or units in addition to feeding the electromagnetic valve control. Furthermore, in normal operation, with the DC/DC converter switched off, it is also possible to damp the flow in the engine in order to minimize eddy current losses. Nevertheless, with the DC/DC converter switched on, the electromagnetic valve control can be supplied.